For the aforementioned modem its vendor ALLNET provides such tool (enclosed) and shared it with one of the TO users who posted a sharing link (allegedly with permission of ALLNET) in the Turris Forum.
Testing the tool (EBM mode) it turned out (via tcpdump on TO's eth1) that the tcp packets sent from the client running the tool are received @ TO's eth1 but apparently deadending (no response) there. Thus this feature suggestion.

About the tool - it appears to have been coded by and originating from the modem's chipset designer. In W10 v1809 it should not be run from a restictive desktop but a less restrictive path. It requires MS.NET/Framework/v4.0 or above and WinPCAP LIbrary/Utility. Upon first execution of DSLmonitor.exe registers some dlls to the system.
I had no issue with its execution in a W10 _x64 v1809 environment.